1. Field of the Invention
This invention relates generally to dynamic magnetic information storage or retrieval and more particularly to compensating for the physical changes in flexible disk media due to temperature and humidity when operating with high track densities.
2. Description of the Prior Art
The computer industry has made extensive use of disks for data storage which include rigid and flexible or floppy disks. The disks are generally made of a very thin plastic base with a magnetic oxide coating and are rotated during operation. The data is generally recorded on a plurality of relatively closely spaced tracks. A read-write head is selectively moved to selected tracks to read or write data on the tracks.
One of the ways commonly used in rigid disk technology to position the read-write head over a selected track involves the use of a grating having spaced indicia or marks thereon corresponding to the track positions on the record medium. A sensor, which may be a light sensor, is used to detect the positions of the marks. The sensor is moved in steps across the grating to a particular preselected mark representative of the position to which the read-write head is to be positioned. The read-write head is moved across the record medium concurrently with the movement of the sensor over the grating until the sensor stops at the selected mark on the grating thereby simultaneously positioning the head at the desired track.
The spacing between tracks on the flexible or floppy disks in many systems is typically 0.017 inches as is well understood. The amount of data which may be recorded is dependent upon closer spacing of a larger number of tracks. When the spacing is typically 0.017 inches, increasing the number of tracks with closer spacing presents limitations with respect to positioning the read-write head. This is especially true when, as is generally the case, the disks are subject to physical changes which produce dimensional variations as a result of changes in the environment such as temperature or humidity.
In prior art systems which have utilized a grating with markings thereon to position a read-write head, the grating has been composed of fixed or rigid material which is substantially immune to dimensional changes. However, the flexible disk used as the record medium normally does change in dimension in response to variations in temperature or humidity. These changes in the disk dimensions cause the physical positions of the recorded tracks on the disk to change also. Thus, even though the sensor is positioned over a select mark on the fixed grating, the read-write head may not be precisely positioned over the track to be selected on the disk. If the misalignment is too great, the read-write head may actually be positioned between two adjacent tracks.
With the tendency towards higher track densities in floppy disks, the alignment of the read-write head becomes acute and small dimensional changes in the disk could result in the read-write head actually being positioned over the wrong track.
The foregoing illustrates limitations of the known prior art. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations as set forth above. Accordingly, a suitable alternative is to provide a device for compensating for the physical changes in flexible disk media due to temperature and humidity when operating with high track densities.